Double-contact cam mechanisms



April 10, 1956 M. GOLDBERG DOUBLE-CONTACT CAM MECHANISMS 3 Sheets-Sheet 1 Filed June 30, 1952 INVENTOR MICHAEL GOLDBERG April 10, 1956 M. GOLDBERG DOUBLE-CONTACT CAM MECHANISMS S Sheets-Sheet 2 Filed June 30, 1952 FIG. 4

INVENTOR MICHAEL 60L DEE/7G ATTORNEYS April 10, 1956 Filed June 50, 1952 FIG. 5

M. GOLDBERG DOUBLE-CONTACT CAM MECHANISMS 3 Sheets-Sheet 3 INVENTOR MIG/ME L 60L DEE/P6 m ATTORNEYS United States Paten 2,741,152 'nouiiL'E-cbNTAcT Michael Goldberg, Washington, 'D. C. Appntsaon time so, 1952jsri51 "No. 296,596 '6 Claims. c1. 74-44 (Granted under- Title 35, U. is. Code (195 2), sec. 266) The invention described herein maybe manufactured andus'ed by or for the Government of the United States of America for governmental 'pur eses Without the payrn'ent of any royalties thereon or therefor. v This invention relates to devices for changing rotation into angular oscillation and more particularly to multilobed cams having two-legged followers making double contact with the cams.

The familiar Scotch yokem'echa'nisin eonverts uniform rotation into sinusoidal oscillation along "a "straight line and has a follower making double contact with an eccentrically mounted circular cam. This principle is utilized 'to convert I rotation into angular oscillation in the-patent to H. J. Rober, No. 911,073, p'atemed February 2, 1909.

Heretofore, the use of a convex multilobed cam with a two-legged angular follower, each leg of which makes and maintains Contact 'with the cam at all times has not been known. The multilobed cams of this invention coact with a follower having angularly disposed legs, the inner surfaces of which are substantially fiat, and which surfaces are always maintained in contact with the contour of the cam. By virtue of this double contact the follower is positively oscillated by said cam.

In Qh'e prior art, contact between 'multilob ed cams and a single contact follower has been maintained by use of springs or the like. Rollers have been utilized on the follower to replace sharp point contact with the surface of the cam. The cams and followers of this invention have the advantage over the prior art in that the cam positively drives the follower at all times, and there is, therefore, no 'possibility of vibration such as may result when the contact between the cam and the follower is maintained by a spring. Further, since the contours of the cams of this invention, during the course of a complete revolution, directly contact a largeportion of the substantially fiat planar faces of the two legs of the follower, the wearing of the surfaces of the followers is greatly reduced as compared with the wear which results from the Concentration of loads on the relatively small pin tl'e of a roller.

It is, therefore, an object of this invention to provide 'a device for converting rotation into angular oscillation.

It is afurther object of this invention to provide a multilobed cam and a two-legged follower which follower makes double contact at all times with the contour of the cam.

it is an additional object of this invention to provide a family of convex multilobed can-1s making double contact at all times with the angularly disposed legs "of a family of cam followers.

It is a further object of this invention to provide a double contact substantially plane-faced'foll'ower driven by a convex 'mul-tilobed cam so that the follower oscillates angularlyabout its axis of oscillation, or its pivot.

Still another object of this invention is to provide a cam and double contact follower of rigid construction, so constructed and arranged that any desired integral ICE number of angular oscillations may be imparted to the follower for each revolutio'nof the cam.

Other objects of this invention willbe apparent from a consideration of the following specification when considered in connection with the annexed drawings in which:

Fig. 1 shows diagrammatically one form of a cam and double contact follower; Fig. 2 showsan elevation of a cam of a more general form'and its follower; i v

Fig. 3 shows an elevation of a two-lobed earn of a simpler form and its follower; i

Fig. 4 shows an elevation of 'a three-lobed cam and its follower and Fig. 5 shows an elevation of a four-lobed cam and its follower.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 a diagrammatic illustration of a multilobed cam and double contact follower which forms the subject of this invention.

It can be shown mathematically that the only angles a '(ekhre'ssed in radians) which can be used for double contact cam followers 'of this invention are defined by the equation where a/b is a proper fraction in its lowest terms and where a is odd. The contours of the surfaces of the 'multilobed cams of this invention may have a wide variety of shapes, the most general of which may be described by an equation 'of the form (2) arccos )(0) arccos p(6+1r/b)=1ra/b where, referring to Fig. 1, O is the origin for Cartesian coordinates X and Y, tangents T and F are a diagrammatic illustration of a two-legged follower, C is a diagrammatic "illustration of the contour of a multilobed cam D, and 'p(5) is the distance from the origin 0 to line T which is tangentgto the contour C of the cam D and intersects the X axis at an angle equal to 6. The

distance from the center of rotation or 'origin O of the cam D to the center of oscillation O of the follower F is taken as unity. The distance 12(6) from the origin 0 to the line T may vary in an arbitrary way in the interval from '0'=0 to 6:1r/b. Equation 2 then defines the distance 12(6) from the origin to the line T in the interval from 6:1r/b to 0:21r/l7 and similarly for all other intervals around the circumference of the cam. For a practical contour it is necessary to preserve the continuity of 'p(6), and to insure convexity it is necessary that the curvature of the surface, which is equal "to 12(6) +p"(0), where indicates thesecond derivative,

Segments 16 and 17 of contour 12 are determined by the points of intersection 18 and 19 between contour 12 and a coordinate axis 20 through axis of rotation 22 of cam 11 The curve which describes the contour of segment 16 is any arbitrary convex curve which satisfies Equation 2. Segment 17 is then made identical to segment 16. In other words contour 12 of cam 11 is made up of a whole number of identical portions, or segments, which repeat periodically.

One of the simplest families of cams of this type is described by the equation where n is a constant angle arbitrarily taken small enough to insure the convexityof the curve. In this case the value of must satisfy the equation For example, contour 30 of cam 31 of Fig. 3 is obtained when a=1, b=2, and q5=18. The range of values that (1: may take in this case is from 0 to 90 The angle a is then determined by the equation u:1r(l /2)=9O Four-lobed contour 70 of cam 71 shown in Fig. 5 is obtained when b=4, (7:3 and =l 30'. The range of values that 5 may take in this case is from 0 to l 36'. The angle at determined by the two legs of the follower is found from the equation Referring to the cam 11 of Fig. 2, the most general case, the contour 12 is a periodic curve, that is, it is made up of a whole number of identical portions. Similarly contours 3b, 559, and '79 of cam 31, 51 and 71 of Figs. 3, 4 and 5 are periodic curves. In addition the contours of cams 31, 51 and 71 have two or more axes of symmetry. it should be noted in the simpler cases, that there are as many lobes as there are axes of symmetry. The cam 11 of Fig. 2, however, has no axis of symmetry. Thus it can be seen that contours of the cams of this invention are periodic curves. Contours of the more general case, such as will satisfy Equation 2, need not be symmetric about any axis, while contours of the more simple case, which satisfy Equation 3, are symmetric about a number of axes equal to the number of lobes formed by the contour of the cam.

Referring again to Fig. 2, in which there is shown one form of the invention, cam 11 is mounted on a pivot 21 so as to rotate about its axis of rotation 22 which is also the axis of pivot 23. Pivot 21. comprises means for mounting cam 11 and for imparting rotation to cam 11 from a power source which is not illustrated. A follower mounted on a pivot 23 has angularly extending legs 13 and 14, whose interior faces 24 and 25 are substantially flat planes disposed at an angle,'a, of 90, as explained above, and with the planes determining said faces intersecting at axis of oscillation 26 of follower 15 which is also the axis of pivot 23. Pivot 23 comprises means for applying the oscillation of follower 15 to a load which is not illustrated. The distance between axis of rotation 22 and axis of oscillation 26 is fixed so that the faces 24 and 25 of the legs 13 and i4 always contact the contour 12 of cam 11. in the position illustrated the faces 24 and 25 Contact contour 12 at points 27 and 28. In the embodiment illustrated the spacial relationship between axis of rotation 22 and axis of oscillation 26 is also fixed so that rotation of cam 11 will cause follower 15 to oscillate.

Rotation of cam 11 through 180 about axis of rotation F 22 will cause follower 15 to execute one complete angular oscillation about axis 26. An additional rotation of cam I} the faces 24 and 25 of follower 15 and contour 12 of cam 11,'wil1 move along faces 24 and 25, whereby, the wearing of these faces due to friction and pres-sure is not concentrated, thus contributing to a longer trouble-free period of operation of the device.

In Fig. 3 there is shown another form of the invention. The elliptical cam 31 has two lobes, 32 and 33 respectively, two axes of symmetry, and an axis of rotation 35 which is also the axis of pivot 36. Pivot 36 comprises means for mounting said cam 31 and for imparting rotation to the cam 31 from a power source which is not illustrated. Follower 37 mounted on a pivot 38 has an angularly extending legs 39 and 40, the interior faces 41 and 42 thereof, being substantially flat planes disposed at an angle of 90, as explained above, and with the planes determining said faces intersecting at the axis of oscillation 43 which is also the axis of pivot 38. Pivot 38 comprises means for applying the oscillation of follower 37 to a load which is not illustrated. The distance between axis of rotation 35 and axis of oscillation 43 is fixed so that the faces 41 and 42 of legs 39 and always contact the contour 30 of the cam 31. In the position illustrated, the faces 41' and .2 contactcontour 30 at points 45 and 46, respectively. The spacial relationship between axis of rotation 35 and axis of oscillation 43 is also fixed so that rotation of cam 31 will cause follower 37 to oscillate. Rotation of cam 31 through 180 about its axis of rotation 35 will cause follower 37 to move angularly to the two extreme positions shown in the dotted lines and return to the position shown in the solid lines. An additional 180 of rotation of cam 11 will result in an additional complete angular oscillation of follower 37 about its axis of oscillation 43. V

In Fig. 4 there is illustrated a three-lobed cam 51. The cam 51 has three lobes 52, 53 and 54 and is mounted for rotation about an axis of rotation 55 which is also the axis of pivot 56. Pivot 56 comprises means for mounting cam 51 and for imparting rotation to said cam from a power source which is not illustrated. A follower 57 is mounted for oscillation about an axis of oscillation 58 which is also the axis of pivot 59 with which the follower 57 oscillates. Pivot 59 comprises means for applying the oscillations of. the follower to a load which is not shown. Angularly disposed legs 60 and 61 of follower 57 have substantially flat planar interior faces 62 and 63. The distance between axis of rotation 55 and axis of oscillation 53 is fixed so that the faces 62 and 63 of legs 60 and 61 will always contact the contour 50 of cam 51. In the position illustrated, faces 62 and 63 contact contour 50 at points 64 and 65. The interior faces of the follower subtend an angle of 120, as explained above, the apex of the angle coinciding with the axis of oscillation 58. The spacial relationship between axis of rotation 55 and axis of oscillation 58 is fixed so that rotation of cam 51 will cause follower 57 to oscillate. Rotation of cam 51 through 120 will result in one complete oscillation of follower 57; hence rotation through 360 will result in three complete oscillations of the follower about its center of oscillation.

In Fig. 5 there is disclosed a four-lobed cam 71. The cam 71 has lobes 72, 73, 74 and 75 and is mounted for rotation about an axis of rotation 76 which is also the axis of pivot 77. Pivot 77 comprises means for mounting cam 71 and for imparting rotation to the cam from a power source which is not illustrated. A follower 78 has angularly disposed legs 79 and 80, the interior, substantially planar surfaces 81 and 82 of said legs, subtending an angle of 45 as explained above, and the apex of the angle coinciding with the axis of oscillation 83 of the follower 73. The axis of oscillation 83 is also the axis of a pivot 84 which pivot comprises means for applying the oscillation of follower 78 to a load which is not illustrated. The distance between axis of rotation 76 and axis of oscillation 83 is fixed so that the inner surfaces 81 and 82 of the legs of the follower 78 always contact the surfaces of the contour 70 of cam 71. In the position illustrated, faces 81 and 82 contact contour 70 at points 85 and 86. The spacial relationship between axis of rotation 76 and axis of oscillation is fixed so that rotation of cam 71 will cause follower 78 to oscillate. The turning of cam 71 through 360 will, of course, cause the follower 73 to execute four complete oscillations.

In the explanation of the operation of the embodiments illustrated it has been assumed that the cam rotates to oscillate its associated follower. It is of course obvious that the cam may be held stationary and the axis of oscillation of the follower rotated around said cam to cause the follower to oscillate. Furthermore there may be limited movement of the axis of oscillation of the follower when the cam is rotated. It is only essential that the distance between the two axis be maintained constant or fixed.

Obviously, many modifications and variations are possible in the light of the above teachings. It is, therefore, understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In combination, a convex multilobed cam having an axis of rotation, the contour of said cam being a periodic curve, means mounting said cam for rotation about its axis of rotation, a two-legged follower having an axis of oscillation, the legs of said follower having substantially plane interior faces, the planes determining said faces intersecting at said axis of oscillation, and means mounting said follower for oscillation about its axis of oscillation, the contour of the cam, the angular relationship of said plane interior faces and the spacial relationship between the axis of rotation and the axis of oscillation being such that the substantially plane face of each leg of the follower contacts the contour of the cam throughout a complete revolution of said cam, whereby the follower oscillates about its axis of oscillation when the cam is rotated about its axis of rotation.

2. A device for changing rotation into oscillation comprising a cam having an axis of rotation; the contour of said cam being substantially described by an equation of the form the axis of rotation being the origin of a set of Cartesian coordinates for the equation, 12(6) being the distance from the origin to any line tangent to the contour of the earn, being the angle the line makes with one of said coordinates a/ b being a proper fraction and a being odd; means mounting said cam for rotation about its axis of rotation,

arccos p(0) +arccos 6 a cam follower having an axis of oscillation and two legs, the inner surfaces of said legs defining substantially fiat planes, said planes intersecting at said axis of oscillation and defining an angle a determined by an equation of the form a=1r(1ll/b) and means mounting said follower for oscillation about its axis of oscillation, the means for mounting said cam and said follower being located so that the inner surface of ea h leg of the follower contacts the contour of said cam.

3. A device for changing rotation into oscillation comprising a cam having an axis of rotation; the contour of said cam being substantially described by an equation of the form the axis of rotation being the origin of a set of Cartesian coordinates for the equation, 1(8) being the distance from the origin to any line tangent to the contour of the cam, a being the angle the line makes with one of said coordinates a/ b being a proper fraction, and a being odd, having a value which satisfies the equation means mounting said cam for rotation about its axis of rotation, a cam follower having a fixed axis of oscillation and two legs, the inner surfaces of said legs defining substantially fiat planes, said planes intersecting at the said axis of oscillation and defining an angle a determined by equation of the form c=7r( 1[l/b) and means mounting said follower for oscillation about its axis of oscillation, the inner surface of each leg of said follower contacting the contour of said cam.

4. The device as claimed in claim 3 in which a=1, 11:2, and the value of is in the range of 0 to 90.

5. The device as claimed in claim 3 in which (1 1, [2:3 and the value of is the range of 0 to 30.

6. The device as claimed in claim 3 in which (i=3, b=4 and the value of is in the range of 0 to 736'.

References Cited in the file of this patent UNITED STATES PATENTS 1,118,411 Granz Nov. 24, 1914 1,943,118 Holmes Ian. 9, 1934 2,095,744 Hanna Oct. 12, 1937 2,611,292 Chandler Sept. 23, 1952 

